From 834789d006d5fa6a7448cfd49ac03bba7da0c527 Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Mon, 20 May 2013 20:16:34 +0200
Subject: [PATCH] Chain kernel frame pointer list with user-space.

---
 sortix/x64/syscall.s | 6 ++++--
 sortix/x86/syscall.s | 5 +++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/sortix/x64/syscall.s b/sortix/x64/syscall.s
index 392683e5..0e574543 100644
--- a/sortix/x64/syscall.s
+++ b/sortix/x64/syscall.s
@@ -33,7 +33,9 @@ syscall_handler:
 	sti
 
 	movl $0, global_errno # Reset errno
+
 	pushq %rbp
+	movq %rsp, %rbp
 
 	# Make sure the requested system call is valid, if not, then fix it.
 	cmp SYSCALL_MAX, %rax
@@ -41,8 +43,8 @@ syscall_handler:
 
 valid_syscall:
 	# Read a system call function pointer.
-	xorq %rbp, %rbp
-	movq syscall_list(%rbp,%rax,8), %rax
+	xorq %r11, %r11
+	movq syscall_list(%r11,%rax,8), %rax
 
 	# Oh how nice, user-space put the parameters in: rdi, rsi, rdx, rcx, r8, r9
 
diff --git a/sortix/x86/syscall.s b/sortix/x86/syscall.s
index db6b9344..346a5cb7 100644
--- a/sortix/x86/syscall.s
+++ b/sortix/x86/syscall.s
@@ -33,6 +33,7 @@ syscall_handler:
 	sti
 
 	movl $0, global_errno # Reset errno
+
 	pushl %ebp
 
 	# Grant ourselves kernel permissions to the data segment.
@@ -53,6 +54,10 @@ valid_syscall:
 	xorl %ebp, %ebp
 	movl syscall_list(%ebp,%eax,4), %eax
 
+	# Point the %ebp register to the pushed user-space %ebp above.
+	movl %esp, %ebp
+	addl $4, %ebp
+
 	# Call the system call.
 	pushl %esi
 	pushl %edi